Abstract: Inversion of particle size distribution from scattered light intensity distribution with laser particle size analyzer based on Mie theory is a typical process for solving inverse problems, in which particle size inverse algorithm is critical. Projection iterative inverse algorithm is sensitive to noise and it causes particle size measurement distortion in actual applications. Vondrak-s smoothing algorithm was adopted to conduct smoothing processing to Projection inversion, and simulation study on algorithm applications was carried out by writing testing software on VC++6-0. By analyzing and comparing the inversion results obtained before and after smoothing processing, it is concluded that the introduction of Vondrak data smoothing processing algorithm effectively improves the anti-interference ability of Projection inversion. The experiment result shows that the inversion result obtained after Vondrak data smoothing processing reflects the real particle size distribution and meets the measurement requirements on stability, reliability, high precision and strong anti-interference capability for modern powder production industry.